Begin by downloading Joomla! 2.5 onto your computer. Then decompress it and upload the contents of the folder (not the folder itself!) to the destination folder on your instance.

For example: If you want your site to be visible at www.example.com, then you will need to upload the files to the www.example.com/htdocs/ virtualhost folder of your instance.

Finally, in order to limit the possibility that someone might gain unauthorized access to your website, create a file called configuration.php using your favorite simple text editor and put it in the same directory where you transferred the other files, and set its permissions to 777 (see your FTP client's help documentation for assistance changing the rights of a file, though usually right-clicking on it will bring up the option).

Once this operation has been realized, type the address of where you uploaded the files to in your web browser's address bar. For example, if your put your Joomla! files in the virtual host www.example.com then type the address http://www.example.com in your browser's address bar.

You will then see an installation page asking you to choose a language.

The next step will check the PHP that is present on your instance. The first list must be totally green before you can install Joomla! and the second one is only a verification of the compatibility for potential extensions that you might use with Joomla!.

The next step is just the usage conditions that you should read, and if you accept, then proceed to the next page.

Now, you are asked for information on your database. If you have not yet made a database for your instance, see this page. For the user, it would be best to create a special user for your database (use the permissions option once you are logged into PHPmyAdmin and in the admin page for the database you want to use for Joomla)

Once you have connected to your database, you will arrive at a step that allows you to activate the FTP layer of Joomla! in order to allow you to write the configuration in the corresponding file. This step is not important (since you cannot connect to your instance through FTP), and you have uploaded a “configuration.php” file to your instance and gave it write permissions.

You can just click on “Next” to skip this step. You will then be asked for the general information for your website. Go ahead and fill in the form as desired:

You may get a message concerning a token expiring. Simply click ok to close the pop-up message and then click on “Next” again.

Finally, you will be asked to delete the installation directory in order to make your website more secure. You cannot use the button to remove it because your instance does not use FTP. To remove the file, connect using sFTP and delete it manually.

You're done, have fun!